It is known to provide an oil separation device in a blow by gas passage for returning blow by gas from a crank chamber to an intake system in an internal combustion engine. JP4043825B and JP4353473B disclose that a gas liquid separation chamber provided with a plurality of baffle plates may be incorporated in a head cover formed by combining a plurality of members. As the blow by gas containing oil mist flows from an inlet to an outlet of the gas liquid separation chamber, the blow by gas collides with the baffle plates and changes directions so that the oil mist adheres to the baffle plates owing to the inertia of the oil mist, and is separated from the blow by gas.
JP2016-023631A discloses an oil separation device for an internal combustion engine that includes a gas liquid separation chamber elongated in a prescribed direction and defining a spiral passage. To define the spiral passage, the gas liquid separation chamber of this oil separation device is provided with a plurality of slanted upright walls extending from the bottom wall thereof at a first angle to a direction orthogonal to the prescribed direction in plan view and arranged in the prescribed direction, and a plurality of slanted depending walls extending from the top wall thereof at a second angle to the direction orthogonal to the prescribed direction in plan view and arranged in the prescribed direction, the first and second angles being in mutually opposite senses.
In the case of an oil separation device for an internal combustion engine, an oil separation chamber is typically formed in an engine cover defining a valve actuating chamber in cooperation with the upper surface of the cylinder head, and a gas inlet of the gas oil separation chamber communicates with the valve actuating chamber. Therefore, oil splashed by a moving part in the valve actuating chamber such as a camshaft may be introduced into the gas inlet.